Non-woven fabric laminates are useful for a wide variety of applications. Such non-woven fabric laminates are useful for wipers, towels, industrial garments, medical garments, medical drapes and the like. In heavier basis weights, the laminates are used in recreational applications such as tents and as car covers.
Disposable fabric laminates have achieved especially widespread use in hospital operating rooms for drapes, gowns, towels, foot covers, sterilization wraps, and the like. Such medical fabric laminates are generally spunbond/meltblown/spunbond (SMS) laminates including non-woven outer layers of spunbond polymers and an interior barrier layer of meltblown polymers. Examples of SMS laminates are described in U.S. Pat. No. 4,041,203 to Brock, et al., U.S. Pat. No. 4,766,029 to Brock, et al., U.S. Pat. No. 5,169,706 to Collier IV, et al., U.S. Pat. No. 5,188,885 to Timmons, et al., U.S. Pat. No. 5,464,688 to Timmons, et al., and U.S. Pat. No. 5,607,798 to Kobylivker, et al. which are all incorporated herein by reference.
Some fabric laminates, including the SMS fabric laminates, are substantially water impermeable, yet breathable allowing for water vapor transmission. For example, in an SMS laminate, the internal meltblown barrier layer is porous but still can inhibit the strikethrough of fluids or the penetration of bacteria from the outside of the fabric laminate to the inside. In order for the laminate to perform properly, it is necessary for the meltblown barrier layer to have a fiber size and a pore size distribution that assure breathability of the fabric while at the same time inhibiting strikethrough of fluids and bacteria.
In the past, those skilled in the art have attempted to design meltspun non-woven webs, such as meltblown webs, that have improved liquid repellency. For instance, in the past, fluoropolymers have been added to the polymer during formation of the web in order to improve the liquid barrier properties of the web. Such additives are disclosed in U.S. Pat. No. 5,178,932 to Perkins, et al and in U.S. Pat. No. 5,178,931 also to Perkins, et al which are both incorporated herein by reference. A need still remains, however, for methods and processes for improving the liquid repellency of meltspun webs. A need also exists for laminates containing the meltspun webs that inhibit the strikethrough of fluids.
In general, the present invention is directed to nonwoven webs made from thermoplastic polymers that have improved barrier properties, such as liquid repellency properties. The nonwoven Web can be, for instance, a meltspun web such as a meltblown web or a spunbond web. In accordance with the present invention, in order to improve the barrier properties of the web, a hydrophobic agent is incorporated into the polymer that is used to produce the web. The hydrophobic agent can be, for instance, a polydimethylsiloxane, a guerbet ester, or mixtures thereof.
The hydrophobic agent can be incorporated into the polymer in an amount less than about 10% by weight. For example, in one embodiment, the hydrophobic agent can be incorporated into the polymer in an amount from about 0.5% to about 3% by weight, and particularly in an amount of about 2% by weight.
Webs made according to the present invention exhibit improved liquid repellency properties as evidenced by hydrostatic head values, and improved blood strikethrough properties as exhibited by resistance to blood penetration values. The nonwoven webs can be used alone or can be combined into a laminate.
For example, in one embodiment of the present invention, a hydrophobic agent is combined with a polymer and formed into a meltblown web. The meltblown web is then used to form a spunbond/meltblown/spunbond laminate.
Laminates made according to the present invention can be used in many and diverse applications. For instance, the laminates can be used to form medical garments, drapes, gowns, towels, foot covers, sterilization wraps, and the like. Laminates made in accordance with the present invention can also be used to form various personal care articles, such as diapers, incontinence products, and feminine hygiene products.
Other objects, features, and aspects of the present invention are discussed in greater detail below.
As used herein the term xe2x80x9cmeltblown fibersxe2x80x9d means fibers of a polymeric material which are generally formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers can be carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, et al. which is incorporated herein by reference. Meltblown fibers may be continuous or discontinuous, are generally smaller than 10 microns in average diameter, and are generally tacky when deposited onto a collecting surface.
As used herein, the term xe2x80x9cneck-bonded laminatexe2x80x9d refers to an elastic member being bonded to a non-elastic member while the non-elastic member is extended in the machine direction creating a necked material. xe2x80x9cNeck-bonded laminatexe2x80x9d refers to a composite material having at least two layers in which one layer is a necked, non-elastic layer and the other layer is an elastic layer thereby creating a material that is elastic in the cross direction. Examples of neck-bonded laminates are such as those described in U.S. Pat. Nos. 5,226,992, 4,981,747, 4,965,122, and 5,336,545, all to Morman, all of which are incorporated herein by reference thereto.
As used herein the term xe2x80x9cspunbond fibersxe2x80x9d refers to small diameter fibers of a molecularly oriented polymeric material. Spunbond fibers may be formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appel, et al., U.S. Pat. No. 3,692,618 to Dorschner, et al., U.S. Pat. No. 3,802,817 to Matsuki, et al., U.S. Pat. Nos. 3,338,992 and 3,341,894 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No. 3,542,615 to Dobo, et al, and U.S. Pat. No. 5,382,400 to Pike, et al., which are all incorporated herein by reference. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface and are generally continuous. Spunbond fibers are often about 10 microns or greater in diameter. However, fine fiber spunbond webs (having and average fiber diameter less than about 10 microns) may be achieved by various methods. The spunbond fibers can be monocomponent or multi-component fibers.
As used herein, the term xe2x80x9cstretch-bonded laminatexe2x80x9d refers to a composite material having at least two layers in which one layer is a non-elastic gatherable layer and the other layer is an elastic layer. The layers are joined together when the elastic layer is in an extended condition so that upon relaxing the layers, the gatherable layer is gathered. For example, one elastic member can be bonded to another member while the elastic member is extended at least about 25 percent of its relaxed length. Such a multilayer composite elastic material may be stretched until the non-elastic layer is fully extended. One type of stretch-bonded laminate is disclosed, for example, in U.S. Pat. No. 4,720,415 to Vander Wielen, et al., which is incorporated herein by reference. Other composite elastic materials are described and disclosed in U.S. Pat. Nos. 4,789,699 to Keiffer, et al., 4,781,966 to Taylor, 4,657,802 to Morman, and 4,655,760 to Morman, et al., all of which are incorporated herein by reference thereto.